This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 100 20 177.6, filed on Apr. 25, 2000, the entire disclosure of which is incorporated herein by reference.
1. Field of the Invention
The invention relates to an arrangement for reducing the noise generated by the aerodynamic flow of air over the lifting wings of aircraft, and particularly along the control surfaces such as high lift flaps or slats of such wings.
2. Background Information
A significant portion of the total noise generated by an aircraft in flight is caused by the flow of air along the external contours of the aircraft. A large part of this aerodynamically generated noise is contributed by the flow of air over or along control surfaces of the aircraft. The aerodynamically generated noise is especially significant and causes a disturbing influence in the surrounding environment, particularly in the landing approach of an aircraft, because in the landing configuration, the extended high lift flaps generate additional noise, and this noise is generated and radiated into the environment at a relatively low flight altitude. For this reason, noise level regulations are becoming ever stricter, especially in the vicinity of major airports.
Attempts have been made in the prior art to reduce the aerodynamic generation of noise by aircraft in flight. For example, it is conventionally known to arrange flow stabilizers in the form of winglets on the wing tips or the like, in order to stabilize the air flow, with a hope of reducing the noise in addition to other effects. However, in actual practice, the noise reducing effect of such winglets is rather minimal.
In view of the above it is an object of the invention to provide an arrangement that can effectively reduce the noise generated from the extended control surfaces of an aircraft in flight. The inventive arrangement shall be simple in structure and installation, so that it can be installed in new aircraft and easily retrofitted on existing aircraft. The inventive structure shall be economical in cost, and light in weight, so that it does not cause disadvantages in the manufacturing and operation of the aircraft. Furthermore, the inventive arrangement shall not significantly detract from the proper aerodynamic characteristics of the control surfaces. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages as apparent from the present specification.
The above objects have been achieved according to the invention in an arrangement for reducing noise generated on the lifting wings of an aircraft, and particularly on control surfaces such as high lift flaps, slats, spoilers, ailerons, rudders, and the like. According to the invention, the arrangement includes at least one vortex generator arranged on the outboard and/or inboard ends of the respective control surface. Particularly, the vortex generator may be arranged on a profile side surface or along an upper side edge or a lower side edge of such a profile side surface, or directly on an end line edge at the outboard or inboard ends of the respective control surface. Thereby the vortex generator extends over at least a portion of the profile depth or chord length of the respective control surface at the inboard or outboard end thereof. As further features of the invention, additional vortex generators may be arranged on the trailing edge of a flap, or on the trailing edge of the lifting wing itself. The vortex generator preferably comprises elongated elements that protrude outwardly away from the respective outboard or inboard edge of the control surface, and that may form a rigid comb-like structure, or a flexible brush-like structure.
In a preferred embodiment of the invention, the vortex generators are arranged on the inner and/or outer profile end surfaces of a control surface and particularly of a flap. These vortex generators influence the overall vortex system generated by an aircraft during flight. This vortex system at issue particularly includes a so-called main vortex, which is a relatively large vortex that is generated from and along the gap or discontinuity between the main wing and the control surface or surfaces. This main vortex involves a relatively undisturbed, large-volume vortex flow of air, which radiates a significant amount of noise into the far field of the surrounding environment.
In the inventive arrangement, the relatively small vortex generators arranged along the edges of the control surface purposely generate a greater number of relatively small individual vortices, which break-up and take energy away from the main vortex and thereby reduce the strength of the main vortex without significantly reducing the aerodynamic effect of the control surfaces and particularly the lift effect of the high lift flaps. The noise generated and radiated by the interaction of the various smaller vortex systems with the main surfaces and the surfaces or edges of the flap is significantly less than the noise generated by the undisturbed larger volume vortex system that would otherwise arise without the inventive vortex generators.
A substantial advantage of the invention is that relatively inexpensive and simple measures, with a relatively low construction and installation effort, achieve a significant noise reduction. In this context it is further advantageous, that the vortex generators according to the invention are easily adaptable with little effort, based on various factors such as the wing geometry, selected flight conditions, and the like, so that an efficient noise reduction can be achieved in a very simple and economical manner for various applications. A further advantage of the invention is that the subject vortex generators are rather light in weight, and in general hardly have any negative influence on the overall capacity or operation of the aircraft.